Parental choice with a consideration for public safety. If a school district requires certain vaccines to attend, the choices for parents are to do it, sue them to stop it, find a different school, or run for office and kick them out.
That being said government should also have a threshold to cross showing that required vaccinations actually has some beneficial outcome to protect all kids.
If one kid is vaccinated against the Measles and another is not, so what. The kid with the vaccine is protected if the vaccine works as intended and the kid without it isn't affected negatively by teachers, parents, administrative staff.
I think it also could be argued that it violates HIPPA laws and that one's private medical info is no business of the schools.